ArXiv Galaxy
Stellar Population Bulge * Recent observations show that the stars in the Galactic bulge region comprise several kinematic and chemical components spanning a range in α−enhancement (Babusiaux et al. 2010; Bensby et al. 2010) arXiv:1212.1540 ** Although the bulge region can no longer be described as a single stellar population, it appears to be a mostly old, α-enhanced system whose stars formed over a short period of time early in the life of the Galaxy (Zoccali et al. 2003; Mel´endez et al. 2008; McWilliam & Zoccali 2010; Lecureur et al. 2007; Alves–Brito et al. 2010). * Near–infrared imaging (Okuda et al. 1977), COBE/DIRBE (Dwek et al. 1995; Smith, Price, & Baker 2004) revealed the boxy/peanut morphology of the Milky Way bulge. (Blitz & Spergel 1991; Lopez-Corredoira et al. 2005; Martinez-Valpuesta & Gerhard 2011; Romero-Gomez et al. 2011) arXiv:1212.1540 ** The semi-lenght of the bar is about 3.1-3.5 kpc (Gerhard 2002) ** Axis-ratio is about 1:0.33:0.23 (Dwek et al. 1995) * it is now widely believed from simulations and observations that the boxy/peanut shaped bulges, like the bulge of the Milky Way, are not merger products but formed via instability of the inner disk: see e.g. Combes & Sanders (1981); Raha et al. (1991); Bureau & Freeman (1999). ** Also see: Athanassoula 2008 ** Several authors continue to argue in favour of the importance of dissipational collapse or mergers in the formation of the Milky Way bulge (Zoccali et al. 2008; Babusiaux et al. 2010), based on their interpretation of new chemical and kinematic data. * Recently, a split red clump in the Galactic bulge has been discovered (see Saito et al. 2011; Nataf et al. 2010; McWilliam & Zoccali 2010) * The Galactic bulge appears to show a vertical abundance gradient (e.g. Minniti et al. 1995; Zoccali et al. 2008; Babusiaux et al. 2010) which could be interpreted as evidence for a dissipative formation. Star Clusters * Mass function for present day clusters: *# Globular cluster: nearly universal; log-normal with a peak mass of ~ 2.0\times10^M_{\odot} . (Brodie & Strader 2006; Jornan et al. 2007) *# Young Massive Cluster: simple power-law distribution. (Whitmore & Schweizer 1995; Zhang & Fall 1999; de Grijs et al. 2003) ** Motivated by such a difference between GCs and YMCs, numerous studies have examined the dynamical evolution of the GC MFs to determine whether the initial MFs of GC systems resemble those of YMC systems (Gnedin & Ostriker 1997; Baumgardt 1998; Vesperini 1998; Fall & Zhang 2001; Parmentier & Gilmore 2007; Shin, Kim, & Takahashi 2008) Interstellar Medium Dust *The presence of dust controls the energy input and output from the ISM of galaxies, and aﬀects the spectral shape of the galaxy and the underlining physics of the ISM (Galliano et al. 2005; Dunne et al. 2011) arXiv:1212.1468 ** It is still not well established how dust mass in the ISM evolves (Sloan et al. 2009; Draine 2009; Tielens et al. 2005; Calura et al. 2008) ** Dust grains are considered to be formed in a wide range of objects, particularly stars in the late phase of evolution (e.g. Gehrz 1989). *** Theoretical studies: (Nozawa et al. 2003; Morgan & Edmunds 2003; Ferrarotti & Gail 2006; Zhukovska et al. 2008; Valiante et al. 2009) *** It has been well established that dust grains are formed in the AGB outﬂow (e.g. Habing 1996) *** Recent Spitzer and Herschel studies of SNe and SN remnants (SNRs) show that type-II SNe can form dust, but the reported dust masses range from 10^−4 to 1 M_{\odot} (Sugerman et al. 2006; Meikle et al. 2007; Barlow et al. 2010; Matsuura et al. 2011; Gomez et al. 2012) *** It is difficult to measure the mass-loss rates of stars with very little infrared excess and blue colour cut-oﬀs. However, contributions from very low-mass loss rate stars are not important for the overall global gas and dust budget (Le Bertre et al. 2001; Matsuura et al. 2009) ** Dust grains might grow in the ISM, using stellar dust as seeds (e.g. Tielens et al. 2005; Draine 2009) * Taking near- and mid-infrared colours is an indicator of mass-loss rates (Le Bertre & Winters 1998; Whitelock et al. 1994) arXiv:1212.1468 ** The correlation between colour and mass-loss rates have been established for LMC and SMC carbon-rich AGB stars (Matsuura et al. 2009); for oxygen-rich AGB stars (Matsuura et al. 2012) Stellar Stream * Many stellar streams and substructures resulting from the tidal disruption of satellite dwarf galaxies and star clusters under the gravitational inﬂuence of the Milky Way have been identiﬁed and mapped using deep, large-area photometric surveys (Newberg et al. 2002; Ibata et al. 2003; Majewski et al. 2003; Yanny et al. 2003; Rocha-Pinto et al. 2004; Belokurov et al. 2006; Grillmair & Johnson 2006; Grillmair & Dionatos 2006a,b; Grillmair 2006; Belokurov et al. 2007; Grillmair 2009; Newberg et al. 2009; Willett et al. 2009; Grillmair 2010; Koposov et al. 2010; Rocha-Pinto 2010; Sharma et al. 2010; Li et al. 2012; Sesar et al. 2012). ** Streams and cloud-like substructures have also been observed kinematically via spectroscopic surveys of tracers such as RR Lyrae, M-giants, or turnoﬀ stars (e.g., Vivas et al. 2001; Duﬀau et al. 2006; Carlin et al. 2012; Majewski et al. 2012; Sheffield et al. 2012).